What is an Eco Home?

What do we mean by the term ‘eco house’? It seems there is no single definition.

The nearest we get is: ‘a dwelling that uses materials and (perhaps) technology to reduce its energy needs and its impact on the environment’. Some definitions also include phrases like ‘environmentally friendly’, ‘sustainable materials’, ‘healthy living’. The idea could mean anything from a couple of solar panels to a house built entirely of reused tyres.

It helps to treat this list as a menu rather than a shopping list, picking items best suited to the project and the people building it. If we accept that we cannot reduce our impact on the environment to zero, what makes an eco house is a matter of degree.

A completely standard brick-and-block house with a solar panel on the roof is at least more eco than the house next door.

Neil and Mary Gourlay’s eco house in Dumfries and Galloway draws on the four Rs of sustainability (reduce, reuse, recycle and recover). It incorporates reclaimed railway sleepers (sawn, treated and polished by local craftspeople) for the wooden floors and functional furniture.

A Kachelöfen biomass stove, shown below, heats up the dry-stone wall that runs through the house. The dry-stone wall is made from stones stacked in the corners in a neighbouring field.

The homeowners, a retired farming couple, have also used local sheep fleece to insulate the property — 150mm of sheep’s wool insulation sits behind every wall.

What is the Difference Between Eco, Green and Sustainable?

Green has no real meaning, but otherwise the terms seem interchangeable. ‘Eco’ may be an abbreviation of ‘ecologically sensitive’, and ‘sustainable’ may mean using natural materials from well-managed sources.

In the end they all mean: a house that, by design, minimises its environmental impact. Many eco housebuilders equate eco with energy efficiency, which is another way of saying lower running costs.

Strathclyde University published a paper in 2013 showing that the embodied energy in a house can be equivalent to up to 25 per cent of the total lifetime energy demands of the house.

To be considered ‘eco’, the house design needs to give some consideration to materials and embodied energy.

Key Elements of an Eco Home

Energy Efficiency

Any house with eco pretensions must be energy efficient. Often this is limited to space heating only and simply achieved with more insulation. An eco house needs to address energy consumption wherever it occurs.

Space heating is important, but so too is hot water and electricity consumption.

Materials

A walk around any builders’ merchant will show that there has been a shift towards more sustainable materials. This may have been driven by the (now defunct) Code for Sustainable Homes.

Under the Code, using sustainably sourced materials was a good way of gaining points without impacting on the design or convenience of the house. Now Forestry Stewardship Council (FSC) certified timber seems to be stocked as standard. There is less PVCu around and timber windows and doors are making a comeback.

The availability of natural materials such as hemp, lime, sheep wool and cellulose has also increased as prices have fallen. For the eco builder, reused and recycled are also holy grails.

Some builders have taken the idea of reducing material impacts to their extreme, as in the case of one Passivhaus built in the middle of Cardiff which is entirely demountable. It is a timber frame house that uses no nails or glue, only screws and bolts. At the end of the home’s life everything can be taken apart and the salvaged materials reused.

Historical Eco Home

“My house was built in July 1817,” says the author of this piece, Tim Pullen. “The stone for the walls came from the fields that surround the house; the lime for the mortar was made in a lime kiln about two miles away.

“The timber would have originally come from forests perhaps five miles away; the roof is covered in local slate. Heat is (as it was originally) provided by wood and most of the electricity is today provided by a wind turbine.

“When I bought the house there was no intent to buy an eco house and there has been no conscious effort since to make it ‘eco’. Two hundred years ago there was no option but to use local, sustainable materials.

“Today, for me at least, using renewable energy is commercially and practically sensible. By most definitions, ours is an eco house but it might be said we have arrived there by accident.”

Natural Materials Equal A Healthy House?

People who live in houses built mainly with natural materials say that the house has a better ‘feel’ to it. It is true that there are no known examples of this type of house having ‘sick house syndrome’. This term tends to be associated with buildings using a lot of steel and plastic, and where the occupants feel uncomfortable or even physically ill.

There is a lot of controversy over whether plastics and non-natural insulation and other non-natural materials contain chemicals that can gas-off to the detriment of occupants. However, there is no controversy that natural materials do not contain those chemicals.

The fact that people living in houses using mainly natural materials feel good may just be psychosomatic, but does that really matter? Any doctor will confirm that a psychosomatic pain hurts just as much as a real one and if people feel good then that is a ‘real’ feeling.

Green Roof, Green Walls

A purist eco builder will attempt to replace the ecology that the house stands on. A green roof will usually not support the same plant and animal life that the ground did and will not usually be maintained in the same way that a garden is. It therefore needs specialist planting, which in turn is likely to bring in different insects and other animal life.

A green wall is much the same as a green roof, but vertical and with different plants and is, perhaps, an even clearer statement of eco credentials. They are normally not installed to all the walls of the house, maybe just one wall or even a part of a wall. Even so, they will have a dramatic effect on the fauna using the garden.

Fabric First Concept

Passivhaus is probably the best known fabric first standard, where the envelope of the house is designed to minimise the heat loss of the house, and consequently its energy demands. To some extent, it also addresses the total energy demands of the house and its occupants, but does little to address materials, their energy content, sustainability or recycling.

Energy efficiency is a prerequisite for the eco accolade, and Passivhaus qualifies in that respect. However, there is a danger that this approach reinforces the idea that energy efficiency is the only target for the eco builder.

The fabric first concept takes the builder much further than that.

It deals with insulation, airtightness, thermal bridging, and so on, as well as thermal mass, glazing and orientation. Fabric first considers how the house can be used to heat itself — using the fabric of the house as part of the heating system. If reducing running costs is the only criterion, then fabric first is the way to go.

If the builder is also concerned about CO2 emissions, water consumption, resource depletion and the impact on the local ecology, then Active House may be an option. It is similar to Passivhaus but goes two steps further, by generating at least as much energy as the house consumes and considering the health and comfort of the people living in it.

Renewable Energy

To an extent, this can be considered as a substitute for fabric first. The builder either achieves an energy-efficient envelope or provides low-cost, low-carbon energy from renewable sources. Obviously the two are not mutually exclusive and an energy-efficient house needs less investment in renewable energy.

The key issue is deciding what you actually want to achieve. The budget may dictate that popping a solar thermal panel on the roof is all that can be done. That makes the house more eco than the one next door.

But there are cheaper and more effective things to do.

Airtightness or draught-proofing. For energy efficiency, it offers the best £ for £ return, and in older houses is likely to have the biggest impact on reducing energy consumption. This is likely to cost £300 or less.

Insulation: Thermal efficiency is a core element of any eco home and insulation is a key component of that. Focus on getting the insulation as consistent as possible on the whole envelope.

Recycled materials: The local salvage yard is likely to be a repository of useful (and cheap) materials. Try to break the cycle of buying everything new.

Green the plot: Getting rid of hard surfaces such as tarmac, brick drives and concrete Grass is of little interest to insects, and adds nothing to the ecology. A mixed species, grassed area (with plantain, daisy, chamomile, yellow rattle, maybe some wild flowers) is more interesting to look at and useful to the fauna in the area.

Solar panels: In eco terms, installing solar panels for hot water is the first and least that can be done.

LED lighting: LED lamps are now affordable and have a big impact on electricity consumption.

Glazing: Often the starting point in a refurbishment or renovation is to replace single-glazed windows with double-glazed, and this will have a big impact. Secondary double glazing will cost much less and have almost the same impact on energy consumption.

The Budget Eco Home

Increasing the thermal efficiency with more insulation is a good thing, but sustainable insulation is more expensive. So rather than installing lots of cheap insulation or less sustainable insulation, it might be worth offsetting the extra expense by using cheaper, reclaimed materials from the salvage yard.

The holistic approach (also called Active House) looks at thermal efficiency, just as Passivhaus does. It also considers sustainable materials and the health of the occupants and the local environment. There are cost implications to this approach but the extra cost may be offset by having a slightly smaller house that is also better for the environment.

All projects have a budget and that implies compromise. An eco house is no different.

An Eco Home Built for Under £1,000/m²

Ian and Simone Pritchett self built an energy-efficient home of hemp/lime construction, at a build cost of just £788/m2.

The home has a thermally efficient structure and uses several eco technologies, such as a mechanical ventilation heat recovery system. This means the home has a heat demand of around 2.5kW — around the same as a powerful hair dryer.

Any move away from standard housebuilding methods and towards eco living is a good move. If you are trying to create an eco home, remember that there is no right and wrong approach, only good or better.